Grinding apparatus

ABSTRACT

The invention relates to a grinding apparatus of the type having grinding discs arranged in a housing of which at least one is rotatable and which between themselves form a grinding space for the grinding produce such as wooden chips fed dispersed in an aqueous vehicle to the centre of the space to be forced therethrough in outward direction under strong axial grinding pressure. Under this procedure the temperature of the vehicle is increased which results in evaporation of water which in turn unfavourably affects the produce such as the wooden chips the fibres of which may be locally overheated and miscoloured. To counteract this evaporation of water, ducts are formed in the grinding discs, at least the stationary one for supply of water to the grinding space between the discs. This arrangement is particularly useful when the grinding discs are composed of concentrical elements defining an outwardly decreasing grinding space permitting a highly advanced desintegration of the starting material.

United States Patent 1191 Reinhall GRINDING APPARATUS [76] Inventor: Rolf Bertil Reinhall, Killingevagen l6, Lidingo, Sweden [22] Filed: Feb.-29, 1972 21, Appl. N0.; 230,393

[30] Foreign Application Priority Data Mar. 16, 1971 Sweden 3397/71 52 US. Cl... 241/38, 241/244, 241 259.1 51 1111. C1. B026 7/06 [58] Field of Search 241/38, 41, 42, 46.06, 65,

[56] References Cited Brown 241/38 1 Feb. 5, 1974 Primary Examiner-Granville Y. Custer, Jr. Attorney, Agent, or Firm-Eric Y. Munson et a1.

[57] ABSTRACT The invention relates to a grinding apparatus of the type having grinding discs arranged in a housing of which at least one is rotatable and which between themselves form a grinding space for the grinding produce such as wooden chips fed dispersed in an aqueous vehicle to the centre of the space to be forced therethrough in outward direction under strong axial grinding pressure. Under this procedure the temperature of the vehicle is increased which results in evaporation of water. which in turn unfavourably affects the produce such as the wooden chips the fibres of which may be locally overheated and miscoloured. To counteract this evaporation of water, ducts'are formed in the grinding discs, at least the stationary one for supply of water to the grinding space between the discs. This arrangement is particularly useful when the grinding discs are composed of concentrical elements defining an outwardly decreasing grinding space permitting a highly advanced desintegration of the starting material.

3 Claims, 1 Drawing Figure 1 GRINDING APPARATUS 1 BACKGROUND or THE INVENTION through the space in outward direction under which fed it is subjected to a strong axial grinding pressure produced e.g., by means of at least one hydraulic servo motor acting on the rotatable grinding disc as is evident from e.g., the US Pat. No. 2 964' 250. I

TI-IE PRIOR ART Under the procedure just described an increase of temperature is produced within the space by the developed friction heat which results in an evaporation of water from the dispersion of the fibrous material. The water content of the dispersion or the material is reduced in responseto the escaping quantity of steam which may have an unfavourable effect on the grinding result. This applies particularly to grinding apparatuses Y which have a larger radial dimension of the grinding discs in order to make it possible? to proceed with the disintegration of the fibres to an extensive degree such as from chips to.a finished fibre pulp product. Grinding apparatuses of this kind may have grinding discs subdivided into concentrical sections adjustable in axial direction relative one another'for compensation of the non-uniform wear on the grinding surfaces of the discs as is evident from e.g., the US Pat. application Ser. No. 884 603 filed Dec. 12, 1969 now US. Pat. No. 3,684,200. I

I In particular when the number of such concentrical grinding disc zones is increased to at least three, which can be said to result in effecting the grinding procedure in three steps within one unit, a great quantity of water will escape from the introduced dispersion of grinding produce of fibres or fibre pulp. It has proved to be advantageous in order to obtain the optimum grinding effect in .the space between the grinding discs, to maintain the watercontent constant or controllable as much as possible during the-passage of the produce through the space. The concentration-of the grinding produce in the dispersion must during the progress of the defibration or refining not be increased by more than a few per cents. Too low a water content can especially in the final step cause local overheating of thefibres whereby these fibres become damaged or dark-coloured. Furthermore, in order to obtain a good disintegration effeet, a high concentration of the pulp in the dispersion at the start of the disintegration process between the grinding discs is, highly desirable which substantially limits the margin of water loss resulting from boiling off or evaporation.

OBJECTS OF THE INVENTION One main object of the invention is to eliminate the drawbacks stated hereinbefore.

SUMMARY OF THE INVENTION According to one main feature of the invention at least one of the grinding discs which preferably is stationary is formed with ducts for supply of water to the space at one or several places located at the same radial distance or at radially differing distances from the cen# tre of the discs between the inner and outer circumferences thereof. The grinding produce will thus be cooled or the dispersion will be diluted during the defibration or refining thereof during its movement in outward direction between the grinding discs. It is even possible to supply more water than the quantity which is evaporated so that the water content of the pulp is increased during the treatment between the grinding discs. This is especially important when the pulp when entering the grinding disc has a concentration amounting from about 30 to about 40 per cents.

BRIEF DESCRIPTION OF THE DRAWING Further objects andadvantages of the invention will become apparent from the following description of a tion of the grinding apparatus.

DETAILED DESCRIPTION OF THE DRAWING FIGURE Referring now to the drawing, reference numeral 10 denotes a portion of the rigid frame of the grindingapparatus which frame forms a casing within which a shaft 12 carrying a grinding disc 14 is mounted rotatably. The grinding disc carries a plurality of concentrically arranged disc elements, which in the present case are three and denoted l6, l7 and 18, respectively, each of said disc elements being composed of segments secured by screws onto the disc 14 about the circumference thereof. Disposed in the centre may. be a disc 20 which feeds the grinding produce radially outwards.

A stationary grinding disc is composed of three concentrically arranged annular retainer members 22, 23 and 24 for a corresponding number of disc elements 26, 27am 28, respectively, which latter also each are composed of segments. The surfaces facing each other of the grinding disc segments on both grinding discs are in known manner formed with radial and peripheral ribs and grooves .in order to attain the optimum grinding effect.

The grinding produce which may have the form of wood chips or partially dismembered fibre pulp is fed to the inner circumference of the grinding discs through a central channel 30 formed in the stationary frame. From said place the grinding produce is advanced radially outwards between the segments of the two grindingdiscswhich segments between themselves fonn a grinding space which in the illustrated embodiment is composed of three concentric zones 31, 32, 33 which progressively decreases in'width in radial direction. The rotatable grinding disc 14 is subjected to an axially acting pressure from one or several means not shown here, such as hydraulically actuated servo motors in accordance with the disclosure of e.g., the US Pat. No. 2 891 733.

In the illustrated embodiment the three concentric annular holder members 22 to 24 are together with the disc segments 26 to 28 supported by them adjustably relatively one another in axial direction. The outermost annular holder member 24 is in this embodiment-preferably by means of screw joints 36v or similar connecthe annular holder members. 22 and 23 are arranged to be actuated by an adjusting mechanism generally denoted 34 and 35, respectively.

In the illustrated embodiment, the axial adjustment is obtained by providing the opposing surfaces of the annular holder members 23,24 with threads 40 so that the annular member 23 is rotatable relatively to the axially fixed annular member 24. The casing has an annular projection 39 formed with threads 38 which engage corresponding threads on the innermost annular member 22 which thereby also is displaced in axial direction when being rotated. Each of the annular members 22, 23 have at their lateral surfaces facing the casing 10 an annular recess 42 formed with an inner gear ring 44 engaged by a gear wheel 46 mounted on a shaft 48 in the stand 10 and adapted to be rotated by means of a hand wheel. The gear wheel 46 is locked in predetermined position by means of a nut 52. In the illustrated embodiment both inner stationary annular holder members 22 and 23 have a rotation mechanism 34 and 35, respectively, whereas the outermost annular member 24 is rigidly anchored in the casing 10.

Each of the two inner annular holder members 22, 23 is individually displaceable axially in one or the opposite direction by rotation thereof by means of the hand wheels 35 and 50 in order thereby to adjust the widths of the spaces 31 and 32, respectively, in relationship to one another and to the uttermost space 33. Hereby a compensation can be effected in a simple way for nonuniform wear on the grinding surfaces in the various grinding space zones 31, 32 and 33, respectively even during operation of the apparatus. Thus, the grinding operation need not be interruptedfor such an adjustment of the spaces. It is essential that in the axial displacement the annular holder members 22 or 23 are advanced in relative parallel direction so that the parallelism between each pair of disc elements forming one of the grinding spaces is always maintained and a uniform grinding effect'around the circumference of the space is ensured even during the adjusting movement. It is obvious that the axial displacement between the. annular holder members 22 to 24 can be effected by means of other devices than those shown here. By providing the grinding apparatus with at least three active grinding zones having adjustable width in relation to one another, the disintegration of the starting material such as chips can be advanced to a substantial degree in one single grinding apparatus so that the final product acquires its final character which normally is obtained by a subsequent refining treatment.

Through conduits 54, 55, which may be controlled by valves 56 disposed therein, water is supplied under pressure to axial channels 58 formed in the casing and connected to one or the otherof said conduits, which channels each open into an annular channel 60 formed on that side of each of the outer annular holder members 23, 24, respectively, which faces the frame. From the channel 60 one or several connection channels 62 extend to an additional annular channel 64 in each of the two annular holder members which spread water around the circumference of the disc and to the spaces 32 and,33, through tolerances 66 between the grinding discs, which tolerances form substantially axially extending ducts. Hereby that water, which during the grinding operationis evaporated in the space is replaced wholly or partially. The supplied water has preferably lower temperature than that temperature which prevails in the space so that the water serves the dual function of increasing the water content of the grinding produce or the fibres and as coolant. It should be observed that the space in the final zone, i.e., between the outermost grinding segment sections 18 and 28 may have a width of some hundredths of l millimeter only, for which reason a loss of water during the separation of the fibres and the fibrillation of the fibres proper is especially perceptible as a result of the subdivision of the spaces of the grinding zones into a plurality of subzones and the adjustability of said spaces in order always to obtain a maximum of effective treatment. The quantity of water supplied to the uttermost space 33 may be equal or greater than that supplied to the intermediate space 32. As is generally known, the circumferential dimension of the space increases with the square of the radius.

In the casing there may prevail a pressure either below or at or above atmospheric pressure and a temperature in accordance therewith.

The invention is also applicable to grinding discs which are not adjustable in relation to one another during operation, although the illustrated embodiment with adjustable grinding discs is especially advantageous due to the feature that the grinding spaces by the additional supply of water to the interior thereof makes it possible to maintain the grinding effect at a maximum level over the entire radial extension of the grinding discs.

While one more or less specific embodiment of the invention has been shown and described, it is to be understood that this is for purpose of illustration only and that the invention is not to be limited thereby, but its scope is to be determined by the appended claims.

What is claimed is:.

l. A grinding apparatus comprising:

a. a housing;

b. a pair of grinding discs arranged within said housing defining between them a grinding space for defibering and refining vegetable material and similar produce;

0. at least one of said grinding discs being stationary and comprising a plurality concentrically arranged disc segments and holder members for said segments; I 1 g (1. said segments being spaced from one another in a radial direction to provide ducts extending substantially axially therethrough, and;

e. means for supplying liquid to said stationary disc and to said grinding space during the grinding operation comprising:

i. a plurality of passages in said holder members and;

.ii. a plurality of radially spaced annular channels defined between said holder members and said disc segments adapted to supply liquid to said grinding space through said ducts.

2. A grinding apparatus according to claim 1 in which the vegetable produce is fed centrally through said stationary disc and said disc segments form separate zones in said grinding space successively decreasing in width towards the periphery of the discs.

3. A grinding apparatus according to claim 2 in which said holder members are axially adjustable.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent: No. 3,790,092 Dated r ry 5, 1 7

Inventor-(S) ROLF BERTIL REINHALL and tizt zag grflitizzjs22:26:??? appears in the above-identified patent e hereby corrected as shown below: Claim 1. Par. c. (line 44) Cancel "at least" I Par. d. (line 49) "ducts" is changed to "a duct" Par. d. (line 50) "therethrough" is changed to "therebetween" Par. i. (line 54) is corrected to read: "passages extending axially through said stationary disc and through the adjacent holder member" Par. ii. (lines 56-59) is corrected to read:"circumferential annular channels defined between said holder members and said disc segments adapted to supply liquid from' said passages to said grinding space through said duct".

Signed and sealed this 21st day of May 1971;.

(SEAL) Atte st:

WARD 1*1.FLETGIZEH,JR. v I G. MAHSl-IALL' DANE Attesting Officer Commissioner of Patents FORM PO-1050 (10-69) USCOMM'DC 60376-P69 54 GOVERNMENT PRINTING OFFICE I9. O-Qll-SSL 

1. A grinding apparatus comprising: a. a housing; b. a pair of grinding discs arranged within said housing defining between them a grinding space for defibering and refining vegetable material and similar produce; c. at least one of said grinding discs being stationary and comprising a plurality concentrically arranged disc segments and holder members for said segments; d. said segments being spaced from one another in a radial direction to provide ducts extending substantially axially therethrough, and; e. means for supplying liquid to said stationary disc and to said grinding space during the grinding operation comprising: i. a plurality of passages in said holder members and; ii. a plurality of radially spaced annular channels defined between said holder members and said disc segments adapted to supply liquid to said grinding space through said ducts.
 2. A grinding apparatus according to claim 1 in which the vegetable produce is fed centrally through said stationary disc and said disc segments form separate zones in said grinding space successively decreasing in width towards the periphery of the discs.
 3. A grinding apparatus according to claim 2 in which said holder members are axially adjustable. 